Fix broken links and content errors in the English documentation

[soramikan]

Summary

• Fix broken internal links and incorrect anchors across the English documentation.
• Replace the invalid Streamer.bot link with its official website.
• Update links that referenced removed or relocated documentation pages.
• Correct invalid Docusaurus admonition directives.
• Fix incorrect node names and typographical errors in blueprint tutorials.
• Clarify inaccurate instructions and descriptions in the data folder guide.

Details

This updates links to the current character mod, onboarding, watcher, and data input documentation. It also corrects several content issues, including the Set Character Bone Scale node name, a misspelled Transform label, incorrectly merged list entries, and inaccurate folder and file-type descriptions.

These changes are intentionally kept separate from #123 and modify only the English documentation.

Validation

• yarn typecheck
• yarn docusaurus build --locale en
• Verified that the English build completes without broken-link, broken-anchor, or invalid-directive warnings.
• Verified that the corrected Streamer.bot URL is reachable.